<!DOCTYPE html>
<html>
      <head>
            <meta charset="utf-8">
            <meta name="viewport" content="width=device-width,initial-scale=1">
            <link rel="stylesheet" href="https://cdn.staticfile.net/twitter-bootstrap/4.3.1/css/bootstrap.min.css">
            <script src="https://cdn.staticfile.net/jquery/3.2.1/jquery.min.js"></script>
            <script src="https://cdn.staticfile.net/popper.js/1.15.0/umd/popper.min.js"></script>
            <script src="https://cdn.staticfile.net/twitter-bootstrap/4.3.1/js/bootstrap.min.js"></script>
      </head>
      <body>
            <div class="container">
                  <h2>圆角图片</h2>
                  <p>rounded类可以让图片显示圆角效果：</p>
                  <img src="https://img2.baidu.com/it/u=1845634659,766211561&fm=253&fmt=auto&app=138&f=JPEG?w=800&h=1400" class="rounded" alt="rounded" height="600" width="600">
                  <p>rounded-circle类可以让图片显示圆形效果：</p>
                  <img src="https://img2.baidu.com/it/u=1845634659,766211561&fm=253&fmt=auto&app=138&f=JPEG?w=800&h=1400" class="rounded-circle" alt="rounded-circle" height="600" width="600">
                  <p>img-thumbnail类可以让图片显示圆形效果：</p>
                  <img src="https://img2.baidu.com/it/u=1845634659,766211561&fm=253&fmt=auto&app=138&f=JPEG?w=800&h=1400" class="img-thumbnail" alt="img-thumbnail" height="600" width="600">
                  <p>float-right类可以让图片靠右：</p>
                  <img src="https://img2.baidu.com/it/u=1845634659,766211561&fm=253&fmt=auto&app=138&f=JPEG?w=800&h=1400" class="float-right" alt="float-right" height="600" width="600">
                  <p>float-left类可以让图片靠左：</p>
                  <img src="https://img2.baidu.com/it/u=1845634659,766211561&fm=253&fmt=auto&app=138&f=JPEG?w=800&h=1400" class="float-left" alt="float-left" height="600" width="600">
                  <p>mx-auto和d-block类可以让图片居中：</p>
                  <img src="https://img2.baidu.com/it/u=1845634659,766211561&fm=253&fmt=auto&app=138&f=JPEG?w=800&h=1400" class="mx-auto d-block" alt="mx-auto d-block" height="600" width="600">
                  <p>img-fluid类可以让响应式图片：</p>
                  <img src="https://img2.baidu.com/it/u=1845634659,766211561&fm=253&fmt=auto&app=138&f=JPEG?w=800&h=1400" class="img-fluid" alt="img-fluid" height="600" width="600">

            </div>
      </body>
</html>